code: def __len__(self):
      return self.size
  
file_path: NeMo/nemo/collections/nlp/data/language_modeling/megatron/blendable_dataset.py
imports: import time
  import numpy
  import torch
  from nemo.utils import logging
  from nemo.utils.app_state import AppState
label_desc: Use image node_id 2 for calling the BlendableDataset obj's underlying member method code with example usage: obj.__len__() and returns: self